Herrenknecht has developed a new method called Direct Pipe ®, which combines the advantages of the established Microtunnelling method and Horizontal Directional Drilling technology. A string of prefab pipes is pulled in with only one step. The new Direct Pipe ® method was used for the first time to lay a 464m long steel casing for a water pipeline as well as power and telecommunication cables beneath the Rhine River near Worms (Germany). Breakthrough occurred only 13 days after the beginning of the construction work.

The new Direct Pipe ® method allows the trenchless jacking of a prefab pipe in one step with concurrent excavation of the drill hole. Similar to Pipe Jacking, the excavation of the soil is carried out with a Herrenknecht Micromachine. The navigable Micromachine conveys the excavated material via a slurry circuit above ground. The prefab pipe is pushed forward by the Herrenknecht Pipe Thruster. The pipe transmits the thrust force, required for drilling, to the cutterhead.

The 464m long culvert was laid underneath the Rhine River. Before the culvert construction, one of three mains for the supply of drinking water of Worms, had been located on the old Nibelungen Bridge. For the sake of architectural appearance, an installation of pipes on the new Rhine Bridge should be avoided this time. This is why the construction of the culvert underneath the Rhine River became necessary.

The jobsite was set up on the Hessian side of the Rhine River between the flood protection dam and the riverbank. The Herrenknecht Utility Tunnelling Machine M-215M (AVN1000XC; Ø 1,326mm, max. torque 150kNm), christened “Kriemhild”, bored its way through the Rhine riverbed at a maximum depth of 10m.

Geological formations consisting of silt, sand and gravel were crossed at a maximum pressure of 1.5bar. The Herrenknecht Pipe Thruster “Siegfried” (HK250/500PT) provided the required push force. The Pipe Thruster pushed the 464m long steel pipe (48’’ / Ø 1.20m) with an average thrust force of 80t. The steel casing was welded together on the jobsite. The jobsite team realized advance rates of max. 90m in 24 hours.

After the beginning of the construction work on September 28th, 2007, breakthrough already occurred on October 11th on the other side of the Rhine River in the Federal State of Rhineland-Palatinate – A successful world premiere for Direct Pipe ®.
In brief: This drilling method is not only cheaper than established methods, it also saves time. The increase in know-how allows us to offer our customers even more efficient and environment-friendly solutions.

The 48“ pipe laid near Worms will serve as casing pipe for a water pipeline (Ø 60cm) and twelve ducts for power and telecommunication cables. At the end of November, the entire construction project is scheduled to be completed and the first water could flow through the new transport pipeline to Worms already in December 2007.